Oyapock

The Oyapock or Oiapoque River (/ˈɔɪəpɒk/ or /ɔɪəˈpoʊkiː/; French:Fleuve Oyapock [flœv wɑjapɔk]; Portuguese:Rio Oiapoque [ˈʁiu ɔjɐˈpɔki]) is a 370-km (230-mi)–long river in South America that forms most of the border between French Guiana and the Brazilian state of Amapá. It rises in the Tumuk Humak (Portuguese:Tumucumaque) mountain range and flows into the Atlantic Ocean, where its estuary forms a large bay bordering on Cape Orange.